1. Field of the Invention
The present invention relates generally to a filtration apparatus for separating solid particles from a liquid. More particularly, the invention relates to filtration apparatus for removing particulate contaminants from commercial laundry waste water and to methods for accomplishing the same.
2. State of the Art
State and local governments across the country as well as the federal government have enacted new laws or expanded existing laws to reverse or limit the threat of environmental pollution. These environmental laws are typically directed toward commercial enterprises which create various wastes streams as a by-product of manufacturing products or providing services. The commercial laundry industry and particularly commercial laundromats are specifically affected by environmental laws which limit the amount of suspended solids or particulate contaminants in commercial laundry waste water which can be discharged into the environment. Particulate contaminants in commercial laundry waste water generally consist of lint, hair, dirt and soap scum. To meet the requirements of current environmental laws, the amount of particulate contaminants in commercial laundry waste water must be reduced to an acceptable level before it is discharged into the ground water and/or municipal sewage system.
Co-owned U.S. Pat. No. 5,350,526 discloses a filtration apparatus specifically intended for removing particulate contaminants from commercial laundry waste water. It has at least one porous mesh-like filter bag coupled between an inlet manifold for receiving waste water containing particulate contaminants and an outlet manifold for discharging the particulate contaminants separated from the waste water. The filter bag is agitated by a paddle, so as to prevent the mesh-like material of the filter bag from being clogged. The apparatus is capable of trapping particles as small as 5 microns depending on the filter bag mesh. Those skilled in the art will appreciate that the finer the mesh the more slowly the water will be filtered. One of the challenges in designing a filter for commercial laundry waste water is to be able to accommodate a flow rate of about 12,500 gallons per day.
Co-owned U.S. Pat. No. 5,575,913 discloses a filtration apparatus having a housing, a filter element, an inlet, a first discharge outlet and a second discharge outlet. The housing includes a bottom and an upwardly extending surrounding wall. The filter element is disposed in the housing and spans the surrounding wall with the filter element spaced above the bottom of the housing to define an upper chamber and a lower chamber, and the filter element being angled, preferably 45 degrees from the horizontal, so that one end of the filter element is lower relative to the other end. The inlet is in fluid communication with the upper chamber for receiving waste water containing particulate contaminants. A first discharge outlet is in fluid communication with the lower chamber for discharging filtered waste water. The second discharge outlet is in fluid communication with the upper chamber adjacent the lower end of the filter element for discharging filtered particulate contaminants. The apparatus is capable of trapping particles about 50 microns in diameter (or smaller, i.e. 5-10 microns).
The previously incorporated parent application discloses a filtration apparatus which includes a rectangular tank having an upper baffle and a lower baffle, layers of stone and carbon between the baffles, a water inlet above the upper baffle, and a water outlet below the lower baffle. The tank is approximately 30xe2x80x3xc3x9736xe2x80x3xc3x9760xe2x80x3; the layer of stone is approximately 4xe2x80x3 deep and consists of xc2xexe2x80x3lying on the lower baffle over which is optionally placed a 2xe2x80x3 deep layer of xc2xdxe2x80x3 stone; the layer of carbon is approximately 18xe2x80x3-24xe2x80x3 deep lying on top of the stone layer; the upper baffle is approximately 10xe2x80x3 above the top of the carbon layer; the water inlet is located approximately 15xe2x80x3 above the upper baffle, the water outlet includes two outlets approximately 2xe2x80x3 below the lower baffle; and an air vent is provided 1xe2x80x3 above the water inlet. In operation, waste water enters through the inlet, is spread over the upper baffle and is distributed through the upper baffle onto the carbon at the rate of approximately 5-10 gallons per minute. The carbon layer traps particles which are approximately 10 microns in diameter, and cleaner water exits through the two outlets. The filtration apparatus is preferably used in conjunction with other apparatus including additional filters, holding tanks, a backwash pump and air blower, and a leaching pool system.
The filtration apparatus preferably includes a laundry waste sump, a primary 50 micron static screen filter, an array of 100 micron filter socks, a 9,000 gallon holding tank, a pair of 100 gallon surge tanks, a pair of parallel secondary carbon filters according to the invention, a 5 micron polishing filter, a backwash pump, an air blower, a 6,000 gallon sludge holding tank, one clear well, and a system of four leaching pools. Waste water enters the sump by gravity flow and is pumped from the sump to the primary 50 micron static screen filter which is substantially the same as the filter disclosed in co-owned U.S. Pat. No. 5,575,913. Solids removed by the primary filter are discharged by gravity to the array of 100 micron filter socks where they are dewatered with the water therefrom being returned to the sump. The primary effluent from the primary filter is delivered by gravity to the 9,000 gallon holding (equalization tank). Water from the equalization tank is pumped to the first 100 gallon surge tank from which it flows by gravity to the pair of secondary carbon filters. The effluent from the carbon filters is delivered by gravity to the second 100 gallon surge tank from which it is pumped through the 5 micron polishing filter into the clear well and from there to the four leaching pools. Water from the clear well pool is used to backwash the carbon filters using the backwash pump and the air blower which aerates the backwash water. During backwash, backwash water exiting the carbon filters is directed to the 6,000 gallon sludge holding tank. The carbon filters are operated for 14 to 23 hours continuously and backwashed for ten minutes every day. Each carbon filter operates at a flow rate of approximately 9,000 gallons per day and is backwashed with 450 gallons of water.
A problem which is common to all water filters is that during backwash some solid contaminants remain embedded in the filter media. Over time this lessens the efficiency of the filter, demands more frequent backwashing, and uses more energy to operate the filter. Efforts to increase the efficacy of backwashing usually result in lost filter media. Filter media together with solid contaminants are removed from the filter during backwash. Over time this can be costly as it requires the repeated replacement of filter media.
It is an object of the invention to provide an improved filtration apparatus and method for separating and removing particulate contaminants from a relatively large continuous flow of laundry waste water for discharge of the filtered waste water into the environment, i.e., ground water and/or municipal sewage system.
It is another object of the invention to provide such a filtration apparatus having a filter element for separating particulate contaminants from laundry waste water in which the separated particulate contaminants can be easily and quickly manually or automatically removed from the apparatus without injuring or removing the filter element.
It is still yet another object of the present invention to provide such a filtration apparatus that is easily and inexpensively manufactured, highly efficient in operation, and which requires little lifetime maintenance.
It is yet another object of the invention to improve the backwashing efficiency of such a filtration apparatus.
In accord with these objects which will be discussed in detail below, the filtration apparatus of the present invention includes a rectangular tank having an upper chamber and a lower baffle, layers of stone and carbon between the chamber and the baffle, a water inlet to the upper chamber, and a water outlet below the lower baffle. According to a presently preferred embodiment, the tank is approximately 30xe2x80x3xc3x9736xe2x80x3xc3x9760xe2x80x3; the layer of stone is approximately 4xe2x80x3 deep and consists of approximately xc2xexe2x80x3 stone lying on the lower baffle over which is optionally placed an approximately 2xe2x80x3 deep layer of xc2xdxe2x80x3 stone; the layer of carbon is approximately 18xe2x80x3-24xe2x80x3 deep lying on top of the stone layer; the water inlet is located approximately 25xe2x80x3 above the layer of carbon, the water outlet includes two outlets approximately 2xe2x80x3 below the lower baffle; and an air vent is provided approximately 1xe2x80x3 above the water inlet.
According to the invention, the upper chamber is divided into two parts, one part adjacent to the water inlet and the other part provided with backwash outlets. An air manifold is placed between the carbon layer and the lower baffle, preferably about 2xe2x80x3 under the top surface of the stone. The air manifold is coupled to an air pump for use during backwash. Backwash water inlets are located below the lower baffle.
In operation, waste water enters through the inlet and flows into the upper chamber onto the carbon at the rate of approximately 5-10 gallons per minute. The carbon layer traps particles which are approximately 5 to 10 microns in diameter, and cleaner water exits through the two outlets. During backwash, water is pumped up through the lower baffle, through the stone layer and through the carbon layer into the upper chamber. Air from the air manifold mixes with the water and causes a turbulent action which helps remove solid contaminants from the carbon media. Vertical and angled baffles separating the two parts of the upper chamber allow water and contaminants to exit through the backwash outlets but prevent filter media from exiting.
According to the presently preferred methods of the invention, the carbon filters are operated for 14 to 23 hours continuously and backwashed for ten minutes every day. Each carbon filter operates at a flow rate of approximately 9,000 gallons per day and is backwashed with 450 gallons of water. The air pump coupled to the air manifold preferably delivers approximately 130 cfm of air to the manifold.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.